The Seminiferous Tubules are lined with a complex stratified epithelium called seminiferous epithelium. It consists of two types of cells:
- Spermatogenic cells regularly replicate and differentiate into mature sperm. They are organized in poorly defined layers of progressive development. Most of the immature cells, spermatogonia, rest on the basal lamina. Most of the mature cells, spermatids, attach to the apical portion of the sertoli cells.
- Sertoli cells are the supporting or sustentacular cells. They do not replicate after puberty. They are columnar cells and contain complex apical and lateral processes that surround adjacent spermatogenic cells.
The seminiferous epithelium rests on a basal lamina, surrounded by 3-4 layers of myoid cells and collagen fibrils. The contractions of myoid cells create peristaltic waves that help sperm and fluid to exit the seminiferous tubules.
- Leydig Cells or Interstitial Cells are located between the seminiferous tubules. They are large, polygonal cells. They contain large lipids droplets and have elaborate sERs. They show distinctive rod shaped cytoplasmic crystals (crystals of Reinke), which have refractile structures but their function is unknown. Their mitochondria have tubulovesicular cristae and secrete testosterone during early fetal and adult life. The become inactive between 5 months of fetal life until the onset of puberty.